1. Field of the Invention
The present invention relates to a method for manufacturing an Sn alloy bump that is preferably used for flip-chip mounting for mounting an electronic component on a substrate.
2. Description of the Related Art
At present, methods for mounting the surface of a print substrate by flip-chip mounting using a bump are often employed when electronic components are mounted on the print substrate or the like. As a method for forming the bump, for example, a solder layer is formed on an electrode pad in a resist opening formed on a substrate by electrolytic plating and then the solder layer is melt by performing reflow soldering after removal of resist to thereby form a generally spherical bump.
In recent years, a solder used for bonding electronic components to a substrate has been developed as a lead-free solder material because a lead (Pb)-containing solder material is not preferred in view of environmental aspects. Also, for the material of a bump, it has been thought to use an Sn—Ag binary solder, an Sn—Cu binary solder, an Sn—Ag—Cu ternary solder, and the like having Sn as their main component.
For example, Patent Document 1 discloses a method for forming an Sn—Ag—Cu ternary thin film on a substrate, where the substrate is immersed into a plating bath containing an Sn compound, an Ag compound, and a Cu compound to thereby form the Sn—Ag—Cu ternary thin film by electroplating.
Also, Patent Document 2 discloses a method for forming an Sn—Ag—Cu solder alloy, where Sn—Ag alloy plating is performed and then the resulting multi-layer alloy plating layer is subject to reflow soldering after Sn—Cu alloy plating is performed.